eub | another thing, or think

I ran across a Metafilter thread about the expression "if you think that, you've got another (think/thing) coming." If this is a familiar stock expression to you, which version is familiar, "thing" or "think"? Have you heard the other version?
(Warning: the thread is a mashup of this think/thing with an "is 0.999repeating = 1" debate; skim over unless that's something you enjoy.)

My dad and I agreed that it's a familiar expression, and we'd never heard anyone using the wrong word in it, that would sound bizarre, why is there even a thread about this. But it turned out we disagreed on which word is the right one. The usage in the wild is definitely mixed (it skews "thing" in Google web search, "think" in n-gram books search), and he and I apparently each inferred one correct usage, and assimilated the other one to it, without even noticing the mixedness. Yay language.

(Historically, the "think" version appears to have come first as a stock phrase, carrying a "comically unusual grammar" flavor. The "thing" probably came from rationalizing it, and a small phonetic step given that the doubled /k/ sound in "think coming" is commonly reduced. (The OED2 has an earlier cite for "thing", but since its publication they have pushed "think" earlier.))